JPS6016733Y2 - Secondary combustion chamber of internal combustion engine - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a sub-combustion chamber of an internal combustion engine, particularly a diesel engine, in which a mouthpiece inserted into the sub-combustion chamber is made of a ceramic material.

Constructing the main combustion chamber and sub-combustion chamber of an internal combustion engine with highly insulating ceramic materials increases compression temperature by reducing cooling water loss, reduces ignition delay, and reduces noise and nitrogen oxides (NOx). ) is known to greatly reduce harmful exhaust gas components such as

However, when a cap C made of a ceramic material is simply fitted into the cap insertion recess provided above the bottom surface of the cylinder head H of an internal combustion engine as shown in Fig. 3, the engine is operated at high speed and high load. When this happens, the area around the combustion chamber becomes hot.

At this time, since the ceramic material has a smaller coefficient of thermal expansion than the cylinder head, the fitting part Q between the cylinder head H and the mouthpiece C
A gap larger than that at normal temperature occurs in the outer circumferential direction.

Smoke enters this gap and carbon deposits are generated.

When the engine cools, this gap decreases and the carbon deposit becomes compressed and becomes denser.

Therefore, the heat conduction between the mouthpiece and the cylinder head is good.
The temperature of the cap tends to decrease.

Further, carbon deposits tend to accumulate as the temperature decreases, and as the above cycle is repeated, the carbon deposits accumulate more and more, and if this is significant, the cap C made of ceramic material may be damaged by the compressive force.

Furthermore, in the auxiliary combustion chamber S configured as shown in FIG. 3, there is no compressive force from the lower surface of the cylinder head on the side facing the main combustion chamber M, and there is no compressive force from the inside of the auxiliary combustion chamber and from the piston from the main combustion chamber. Since the gasket G side of the cap C is isolated from the main combustion chamber M by the gasket, it becomes low temperature, so the auxiliary combustion chamber S is bent between the main combustion chamber M side and the gasket G side. There is also a concern that the life of the cap will be shortened due to stress and thermal stress.

On the other hand, a cap made of ceramic material has poor thermal conductivity, and although this property is favorable for heat insulation, the distance between the high-temperature gas passage surface and the low-temperature transmission surface is short, and the contact surface has excellent thermal conductivity. In this case, a large thermal gradient occurs between the high and low temperatures, resulting in thermal stress.

As described above, the occurrence of the carbon deposit and the progress of the deposition are major factors that increase the thermal gradient.

The present invention eliminates these drawbacks and provides a highly durable auxiliary combustion chamber for internal combustion engines. A ceramic acid cap is fixed, a notch is formed in the lower part of the outer circumferential wall of the cap to communicate the annular gap with the main combustion chamber, and a notch is formed in the insertion recess abutment of the cap or the annular gasket to connect the annular gap with the annular gasket. The main feature is that a cutout is provided that communicates with the recess that constitutes the sub-combustion chamber, and an embodiment thereof will be described below.

Reference numeral 1 designates a cylinder body of a diesel cylinder, in which a piston 2 having a main combustion chamber 2a at the top is slidably fitted into the cylinder bore 1a, and a cylinder head is connected to the cylinder above through a rad gasket 3. 4 is placed.

The head 4 has a concave part 5a constituting the upper chamber of the auxiliary combustion chamber 5, a cap 6 made of a ceramic material which is an insulating and fireproof member constituting the lower chamber below the concave part 5a, and a highly compressible annular cap interposed between them. Insertion recess 5b into which gasket 7 is inserted
An injection nozzle 8 is provided above the sub-combustion chamber 5 to inject fuel into the sub-combustion chamber 5.

As mentioned above, the cap 6 is made of a ceramic material that is a heat-insulating fireproof member with excellent heat insulation properties, and has a recess 6a forming a sub-combustion chamber inside and a nozzle 6 communicating with the main combustion chamber 2a.
0.1 to 1rI between the cylinder head insertion recess 5b and the outer circumferential surface of the mouthpiece 6 excluding the fitting part 6c with the cylinder head, so-called upper part of the outer circumferential wall.
FM is which gap t is the annular gap 6d configured to have?
Furthermore, a notch 6 having a gap larger than the annular gap 6d is provided in a part of the lower part of the outer peripheral wall including the thinnest part between the nozzle 6b facing the main combustion chamber 2a of the mouthpiece and the outer peripheral wall.
e, and a cutout 6f is provided in the abutting portion of the cylinder head insertion recess so as to form a gas passage that communicates with the notch 6e through the annular gap 6d.

Since the auxiliary combustion chamber according to the present invention is provided with the cutout part 6f as described above, the side of the mouthpiece 6 made of ceramic material facing the main combustion chamber 2a is released from the pressing force from the highly compressible gasket 7, so that it is compressed. Stress is reduced and durability is improved.

Further, a ceramic acid mouthpiece 6 having an annular gap 6d in the upper part of the outer peripheral wall is fixed to the insertion recess 5b of the cylinder head 1, and the annular gap 6d and the main combustion chamber 2a are formed in the lower part of the outer peripheral wall of the mouthpiece 6. A notch 6e is formed to communicate the annular gap 6d with the recess 6a constituting the auxiliary combustion chamber, and a cutout 6f is provided in the insertion recess abutting part of the cap 6 or the annular gasket 7 to communicate the annular gap 6d with the recess 6a forming the sub-combustion chamber. Therefore, even if smoke that covers carbon deposits enters the annular gap 6d, the high-pressure, high-temperature combustion gas passes through each engine cycle and the smoke is exhausted, so that the carbon deposits do not accumulate in the annular gap 6d. restrained by a hood, thereby
This prevents the cap 6 from being compressed and destroyed due to the accumulation of carbon deposits in the annular gap 6d.

Furthermore, since the annular gap 6d exists, heat conduction through the mouthpiece 6 is restricted and the temperature of the mouthpiece 6 becomes high.The heat conduction path of the mouthpiece 6 is blocked at the portion facing the main combustion chamber, and the portion where the upper and lower gaskets are pressed is Since the heat is concentrated, the heat distribution becomes relatively gentle and the generation of thermal stress is suppressed.

Furthermore, a large amount of smog occurs during low-speed, high-load operation.
Even if no carbon deposit is deposited in the annular gap 6d when the temperature of the notch 5e is low, the notch 6e has a large gap, so a heat insulating layer exists and the cap can be maintained at a high temperature.

Thereafter, when high speed and high load are applied, the temperature of the cap 6 rises and the carbon deposit in the notch 6e can be burnt out.

Further, the cutout portion 6f provided in the abutting portion of the cylinder head insertion recess of the mouthpiece 6 may be provided on the gasket 7 side to obtain substantially the same effect.

Furthermore, since the cap 6 is inserted into the insertion recess 5b via the highly compressible gasket 7, even if the cap 6 protrudes beyond the lower surface of the cylinder head 4 when tightening the cylinder head bolt, the cylinder head will not move as the bolt is tightened. Since the upper surface of the helad gasket 3 is on the same surface, gas sealing performance is further improved.

As described above, the sub-combustion chamber according to the present invention has extremely excellent heat insulation and durability, has a simple structure and is inexpensive, and has the effect of providing a sub-combustion chamber for an internal combustion engine suitable for mass production.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the auxiliary combustion chamber of the present invention, FIG. 2 is a plan view of the same embodiment, and FIG. 3 is a longitudinal sectional view showing a conventional example. 2a: Main combustion chamber, 4 cylinder head, 5: Sub-combustion chamber,
5b = insertion recess, 6: mouthpiece, 6b: spout, 6c: fitting part, 6d: annular gap, 6e: notch, 6f cutout provided in the abutting part of the Niji cylinder head insertion part, 6g: relief Recess, 7: Gasket.

Claims (1)

[Scope of utility model registration request] A ceramic mouthpiece with an annular gap provided in the upper part of the outer circumferential wall is fixed to the insertion recess of the cylinder head, and a notch is formed in the lower part of the outer peripheral wall of the mouthpiece to communicate the annular gap and the main combustion chamber. A sub-combustion chamber for an internal combustion engine, characterized in that the abutting portion of the insertion recess of the mouthpiece or the annular gasket is provided with a cutout that communicates the annular gap with a recess constituting the sub-combustion chamber.